The discomfort experienced from sleeping on collapsible beds, such as sofa beds and portable cots, is well known to most travelers. With reference to FIG. 1, a typical sofa bed 10 includes a sofa frame 11 and a bed frame 12 having two or more pivotally interconnected frame sections 14 including and separated by transverse distal and proximal support bars 15 and 16. Frame sections 14 also include side rails 18 that may cooperate with support bars 15 and 16 to support a fabric mesh or network 19 of lengthwise and widthwise cables 20 and 22 forming a grid-like pattern that defines a deformable bed support plane 23 (FIG. 4) when sofa bed 10 is extended in a bed-forming position 21. The cables 20 and 22 may be individually attached to coil-springs 24, support bars 15 and 16, or side rails 18.
When sofa bed 10 is extended in the bed-forming position 21, side rails 18 of frame sections 14 are typically positioned end-to-end to extend for the length of bed frame 12. Likewise, support bars 16 extend transversely across the width of bed frame 10, and are generally located in proximity to pivot points 25 of bed frame 10. Support bars 15 and 16 are typically positioned below or at the same level as cables 20 and 22.
In some sofa beds 10, support bars 15 and 16 are positioned at or above the bed support plane 23 to retain a flexible pad (not shown) above the cable network. In other sofa beds 10, support bars 15 and 16 are initially positioned below the bed support plane 23. However, use and time cause wear to cables 20 and 22 and coil-springs 24. This wear often causes the bed support plane 23 to drop as much as four inches below the level of support bars 15 and 16. Moreover, such support bars 15 and 16 tend to produce hard, narrow ridges in the typically thin mattresses that are provided to cover bed frame 12. These ridges tend to produce discomfort.
In a sofa bed 10 of a type (not shown in FIG. 1) having frame sections 14 that do not share common support bars 16, the resulting adjacent support bars 15 and 16 are not always at the same level when sofa bed 10 is in the bed-forming position 21. This disparity also tends to produce discomfort.
Despite these and other well known discomforts associated with collapsible beds, relatively few improvements have been suggested. U.S. Pat. No. 3,431,567 of Spitz, et al. describes a series of strap-like linking members to retain one horizontal, transverse cable in proximity to a support bar of the sofa bed frame. Although these straps may prevent seating cushions from sagging toward the back rest of the sofa frame when the sofa bed is collapsed in a seat-forming position, the straps do not prevent sagging toward the middle or the formation of sofa "buckets." Such sofa buckets may cause seated occupants to roll together or may hinder an occupant's ability to get out of the sofa from a seated position.
U.S. Pat. No. 3,892,001 of Schneider describes a flexible panel protector composed of an elongated, rectangular, laminar sheet of flexible, resiliently compressible padding sandwiched between a fiberglass base sheet and a decorative upholstery cover sheet. The flexible panel protector is attached between the front end and front legs of a sofa bed frame section. When the sofa bed is collapsed in a seat-forming position, the panel protector prevents the sofa seating cushions from being abrasively worn by the collapsed uppermost springs. It also conceals and even aesthetically decorates the unsightly uppermost springs in the event a seating cushion is dislodged from the sofa bed, and provides an intermediate cushiony effect between the uppermost springs and the removable cushion to enhance the comfort for seated occupants.
U.S. Pat. No. 1,691,268 of Conrad describes a collapsible bed that employs large partially detachable, flexible pads secured by straps to the bed frame. When the bed is collapsed, these pads are wound about rollers that are integral to the collapsible bed.
U.S. Pat. No. 5,008,966 of Lepow describes a sheet having Velcro.TM. (reversibly attachable nylon hooks and adhesive pile fabrics) strips mated to strips on a sofa bed mattress to secure the sheet to the mattress. The Velcro.TM. strips compensate for mattress-sofa attachment points that would interfere with placing a traditional fitted sheet onto the sofa bed mattress. This sheet may remain on the sofa bed when it is collapsed to the sofa-forming position.
U.S. Pat. No. 4,106,137 of Leclerc describes a sofa bed having a pivoting box-shaped frame adapted to receive a spring mattress. A durable flexible sheet cover extends over the mattress and is secured to the frame to hold blankets against the mattress while the sofa bed is collapsed in the sofa-forming position.
Despite the above-mentioned innovations in sofa-bed design, sofa beds still exhibit sagging and produce substantial discomfort as a consequence of the placement of rigid support bars transverse to the length of the bed.